The present invention relates to automotive powertrain systems. More particularly, the present invention relates to an exhaust gas recirculation system using selective fuel and EGR supply scheduling.
The exhaust gas of internal combustion engines contains various amounts of unburned hydrocarbons, carbon monoxide and nitrogen oxides. Emission of these materials to the atmosphere is undesirable. The problem is more acute in urban areas having a high concentration of motor vehicles. During recent years, researchers have investigated extensively means of reducing exhaust emissions. This research has been quite fruitful. As a result, present-day automobiles emit only a fraction of undesirable materials compared to those of less than a decade ago.
There are many methods for reducing exhaust emissions. One such method is exhaust gas recirculation (EGR) systems. These systems are employed in automotive vehicles in order to help reduce nitrous oxide emissions. Such systems typically employ an EGR valve that is disposed between the engine exhaust manifold and the engine intake manifold, and operable, when in an open position, to recirculate exhaust gas from the exhaust side of the engine back to the intake side. Unfortunately, components left in the exhaust gas due to incomplete combustion may leave deposits within the EGR, induction, and combustion systems. Unburned carbon or other substances contained in the exhaust gas tend to stick to and deposit on surfaces exposed to these exhaust gases. This undesired accumulation could result in reduced engine life and performance.
Another technique for reducing emissions involves injecting fuel into an engine cylinder during a post-combustion time period. This post-combustion injected fuel acts as a reductant for the operation of lean nitrogen oxide catalysis to reduce internal combustion engine nitrogen oxide emissions. However, the combination of EGR with post-combustion injection of fuel to reduce nitrous oxide emissions tends to compound the problem with EGR systems. The interaction of post injected fuel and EGR may increase the level of deposition within the EGR, induction, and combustion systems. Because of the nature of their combustion process, this problem is particularly acute in diesel engines.
The disadvantages associated with these conventional EGR systems using post-combustion fuel injection techniques have made it apparent that a new technique for EGR and fuel injection scheduling is needed. The new technique should reduce the amount of undesirable unburned carbon or other substances contained in the exhaust gas from depositing on the EGR, induction, and combustion systems. Additionally, the new technique should increase overall engine life and performance while reducing long term emissions. The present invention is directed to these ends.
It is, therefore, an object of the invention to provide an improved and reliable EGR system using selective fuel and EGR supply scheduling. Another object of the invention is to reduce the amount of undesirable unburned carbon and other substances contained in the exhaust gas from depositing on the EGR, induction, and combustion systems.
In accordance with the objects of this invention, an EGR system using selective fuel and EGR supply scheduling is provided. In one embodiment of the invention, a method for reducing engine deposits in an internal combustion engine, using selective fuel and EGR supply scheduling, includes an engine having a first and second plurality of cylinders. A fuel injection system for injecting fuel into both of said first and second plurality of cylinders is located on the engine. The engine also includes an exhaust gas recirculation system for supplying a portion of the exhaust gases from the engine to both of the first and second plurality of cylinders. During operation, the engine repeatedly combusts fuel in both of the first and second plurality of cylinders. In accordance with the present invention additional fuel is supplied to one or more selected cylinders following each combustion cycle while recirculated exhaust gases are supplied to the remaining plurality of cylinders. In this way, the interaction of post-combustion injected fuel and recirculated exhaust gases is prevented and the amount of deposition of undesirable materials in the engine is reduced.
The present invention thus achieves an improved EGR system using selective fuel and EGR supply scheduling. The present invention is advantageous in that overall engine life and performance is increased while reducing long term emissions.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.